as in treacherous
formal
causing harm in a way that is gradual or not easily noticed
Most people with this insidious disease have no idea that they are infected. an insidious enemy
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Example Sentences
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Recent Examples of insidious
What makes this deal particularly insidious is the trade-off at its core.
—
Joe Wilkins,
Futurism,
10 June 2026
But most of its failures are subtler, more insidious.
—
Katy Waldman,
New Yorker,
10 June 2026
But there is an insidious quality.
—
Rory McDonald,
Fortune,
6 June 2026
Best known for comedy series like Community (2009-15) and GLOW (2017-19), Alison Brie is taking on the role of Evil-Lyn, an insidious enchantress who serves as Skeletor’s main accomplice.
—
Keith Langston,
PEOPLE,
6 June 2026
See All Example Sentences for insidious
Joe Wilkins,
Futurism,
10 June 2026
But most of its failures are subtler, more insidious.
—
Katy Waldman,
New Yorker,
10 June 2026
But there is an insidious quality.
—
Rory McDonald,
Fortune,
6 June 2026
Best known for comedy series like Community (2009-15) and GLOW (2017-19), Alison Brie is taking on the role of Evil-Lyn, an insidious enchantress who serves as Skeletor’s main accomplice.
—
Keith Langston,
PEOPLE,
6 June 2026
See All Example Sentences for insidious
Recent Examples of Synonyms for insidious
Adjective
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After death, the garden becomes more treacherous.
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For 250 years, between 1565 and 1815, the famous galleon fleet left the port of Manila for the port of Acapulco and back, traveling for months over the treacherous ocean while carrying a lucrative flow of foods, silver, fabrics and culinary traditions.
Adjective
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Available in a style with the same stripes that Paltrow favors, the top offers a subtle pattern that’ll make your outfit pop.
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The square neckline adds a flattering, feminine touch, while the subtle volume in the sleeves gives it a slightly dressier feel than your average tee.
Adjective
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Nadi Jabari, 46, was charged with false personation, unlawful use of a blue light and possession of a firearm during the commission of a felony, the Hillsborough County Sheriff's Office said in a news release.
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Back when King was indicted in the summer of 2025, about 200 of them gathered in a Cleburne conference hall to make plans about how to support the sheriff, and decried the allegations against him as false attacks on King’s character.
Adjective
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Despite criticism over opaque and deceptive practices, prediction markets’ election favorites won most of the time, a Washington Post analysis found; more liquid in betting markets improves their accuracy, economists told CNN, but could carry negative social costs.
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This is the essence of GPS spoofing, in which an attacker floods a GPS receiver with deceptive signals.
Adjective
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This is perhaps the most perfidious practice of this sort of politics.
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Pakistan was a perfidious ‘ally’ in Afghanistan, backing the Taliban while pretending to be our friends.
Adjective
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Govern From Day One In a regulated context, an assistant that produces a confident but incorrect answer carries genuine regulatory and reputational exposure.
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Many argue that signatures are invalid because signers listed incorrect addresses or live outside of the district the candidate wants to represent.
Adjective
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Something told me that there was something wrong.
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The interest rate hypothesis points the wrong direction — the most rate-sensitive occupations, like construction, have the lowest AI exposure.
Cite this Entry
“Insidious.” Merriam-Webster.com Thesaurus, Merriam-Webster, https://www.merriam-webster.com/thesaurus/insidious. Accessed 29 Jun. 2026.
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